Power transmission mechanism



April 1935. c. c. MORLEY 1,999,340

'POWER TRANSMISSION MECHANISM Filed D90. 29, 1933 2 Sheets-Sheet. l

' April 1935. c. c. MORLEY POWER TRANSMISSION MECHANISM Filed Dec. 29,1933 2 Sheets-Sheet 2 Patented Apr. 30, 193 u UNITED STATES PATENTOFFICE POWER TRANSMISSION MECHANISM Cecil Charles Morley, Salisbury,England Application December 29, 1933, Serial No. 704,579 In GreatBritain June 22, 1933 4 Claims. (Cl. 19255) This invention relates topower transmission lustrate, by way of example, one convenient modemechanisms and has for its chief object the proof carrying the inventioninto effect and in vision of a simple and eflicient form of powerWhich:- transmission mechanism adapted to permit the Figure lis avertical sectional view through a torque obtainable from or delivered toa driven power transmission unit embodying three of the shaft to bevaried between predetermined limits. aforesaid cam members.

A further object of the invention is to provide Fig. 2 is a side viewtaken on the line 2-2 of an emcient form of power transmission mechailustrati the formation and the disnism by which a considerable range oftorque position of the cam members and their co-acting variations may beobtained such as will permit elements. a prime mover, designed to carrya normal load,- Figs. 3 and 4 are detail views of one convenient also atleast temporarily to cope with an abnorspeed responsive means which maybe employed mal load, 7 for the relative displacement of the cam mem-Another object of the invention is to provide bers; and an improved formof power transmission mech- Fig. 5 is 'a detail view of a manuallyoperable 15 anism adapted to permit a variable torque to be means whichmay be employed .for such relative obtained from a source ofsubstantially constant displacements. torque, Referring now to theaccompanying drawings According to the invention a power transmisindetail, I denotes a driving shaft which is consion mechanism or unit isprovided comprising nected to a suitable source of power (not shown) thecombination of a driving member, a driven and to the end of which isconnected to move member, a plurality of cams carried by or coutherewitha flywheel 2. To the latter is secured pledto one of the members, aplurality of loaded a housing 3 carrying four angularly spaced pivotelements carried by or moving with the other pins 4 arranged with theiraxes parallel with the member so as to coact'with the cams in aifordaxisof rotationof the shaft I and with their ing a driving connectionbetween the driving and. centres at equal radial distances from thecentre driven members, and means or facilities for enof rotation. Uponeach of the pivot pins 4, are abling the maximum torque setting of themechpivotally mounted three arms 5, 6 and I, which anism to be variedbetween predetermined limits. are suitably loaded or urged towards theaxis Preferably, a kinetic energy storing member of rotation of theshaft I, as for example, by 30 is associated with the aforesaid drivingmember. leaf springs 8 anchored at their middle portions The mechanismis, however, reversible since the by brackets 9 to the housing 3. Theaforesaid aforesaid driven member may constitute the arms are soarranged that each of the sets of driving member, a Similar efiectbeingthereby angularly spaced arms is adapted to coact with Produced y te 0a members acting p the one of a plurality of cam members carried byloaded arms,'there preferably being, under these the shaftto b driv n.That i t say, in th conditions, a kinetic energy storing memberasarrangement illustrated, there are three cams l2, sociated with thedriving member (i. e. the aforel3 and I4 mounted on a. central hub l5which is 'said driven member). keyed to a driven shaft indicated at IS,the ar- 40 In ordertp simplify the description of the inrangement beingsuch that the four arms 5 are 40 vention th":;; nember carryin th c mmember disposed in the same plane as, and are adapted or members will behereinafter referred to as the to coact with, the cam 12, whilst thearms 6 driven member and the member carrying he are disposedin the sameplane as, and are adapted coacting elements or loaded arms will behereto coact with, the cam l3, and the arms 1 are inafter referred to asthe driving member, aldisposed in the plane of, and adapted to coactthough, as mentioned above, the functions of with, th ca II, It is to beunderstood, howthese members y be reVeTSedes ed, ever, that theinvention is not restricted to the means may be provided for enablingthe cam employment of any particular number of members to be displacedrelatively to one anor arms and that the numbers of such elements aother for the purpose of enabling the maximum employed in any particulartransmission'mechatorque setting to be varied. nism will bedependentupon the characteristics In-order that'thefsaid invention maybe clearof the plant ormachinery to which the mechaly understood andreadily carried into effect, the nism is tobe' applied and the nature ofthe torque same will now be more fully described withrefvariationsrequired or the speed fluctuations'pererence to the accompanyingdrawings which 11- missible.

As regards the contours of the cams, it will be observed that eachcomprises foursubstantially equal portions of corresponding outline orconfiguration providing four raised parts or humps the opposite inclinedsides of which are unsymmetrical. That is to say, each hump or raisedportion of each of the cams is made up of an inclined portion A formingone side of the hump and a less steeplyinclined portion B forming theother side of the hump. In operation, the driving shaft and the housing3 are rotated in the direction of the arrow C shown in Fig. 2 so thatthe driving torque tends to urge the spring loaded arms 5, 6 and Iforwardly and up the steeper inclined surfaces A provided on the camsurfaces. The design on the cam members is such that, when the arms areturned about their pivots in opposition to the springs and are caused tomove up the more steeply inclined surfaces A, a reaction is provided onthe cam members tending to drive the shaft to be driven in the samedirection as the driving shaft. On the other hand, while the springloaded arms are being drawn over the less steeply inclined surfaces B,substantially no reaction is produced tending to drive the driven shaftI6, the slope of the cam surfaces B being such that the reaction due tothe load and friction passes approximately through the centre ofrotation.

The cam members I2, I3 and I4 are preferably mounted upon the centralhub -I5 so that they are capable of being moved angularly relatively toeach other and, in instances where the driven shaft is required todeliver, or to be capable of delivering, a large or its maximum torque,the cams are set as shown by the full line in Fig. 2 or, in other words,they are set so that the outlines of the cams I3 and I4 coincide withthe outline of the cam I2. The loading provided on each set of thespring loaded arms is preferably such that the torque required to moveeach set of arms over the steeper inclined cam portions Aissubstantially equal to the torque available from the driving shaft Iwhich together with its associated flywheel 2 are so constructed anddesigned that the energy stored is sufficient for the operation of thetransmission unit within the limits of speed fluctuation permissible.When the load on the driven shaft is such that the torque required is inexcess of ;''the normal torque delivered by the driving shaft, theadditional energy needed to move the spring loaded arms up and over thesteeper portions of the cams is derived from the flywheel 2, it beingunderstood that the arms having been driven to the tops of the camsrequire no further energy to move them over the cam portions B since theslope of these portions in relation to the path of the arms correspondssubstantially with the angle of friction. In the particular arrangementherein described, the length of each of the cam portions B is made twicethe length of each of the cam portions A so that, in moving the threesets of spring loaded arms 5, 6 and I through a complete cycle, with thecams in the position now being particularly described, the averageenergy drawn from the driving shaft corresponds withthat available atthe driving shaft at its normal torque, whilst the torque supplied to oravailable at the driven shaft, when the arms are acting upon the camportions A, exceeds and is in the neighbourhood of three times thatnormally available at the driving shaft.

In instances in which a lower maximum torque setting is permissible ordesired, the cam members I2, I3 and I4 are displaced in relation to oneanother, the limiting position being that in which the cams occupy therelative positions shown by the-fulllines, the dotted lines and thechain-dotted lines shown in Fig. 2. The degree of displacement will, ofcourse, be dependent upon the torque required and, in the limitingposition above referred to with the cam I3 occupying the chain-dottedline position, the cam I4 occupying the dotted line position and the camI2 occupying the full line position there will be little relativemovement between the cam members and their coacting spring pressed arms.With the cams disposed in these relative posi tions, only one set ofspring pressed arms contacts with the steeply inclined cam portions A atany one time. Also, by virtue of the fact that the cam members are soformed that the lengths of the cam portions A are substantially onethirdof the lengths of .the individual cam sections composed of the camportions A and B, or one-twelfth of the cam periphery, and by virtue ofthe fact that the crests of the three cams are angularly displaced fromone another by substantially 30, one set of spring-loaded arms willarrive at the bottoms of the corresponding cam portions A as soon as thepreceding set of arms has reached the tops of cam-portions A with whichthey co-operate.

Under these conditions of operation, the torque imparted to the drivenshaft IE will nearly correspond with the torque applied by the drivingshaft I.

From the foregoing description it will be appreciated that, when theload on the driven shaft I6 is light, the driving member and the drivenmember will rotate at substantially the same speed or under conditionsproviding substantially a direct drive with little or no relativemovement between the cam members and their coacting spring pressed arms.On the other hand, when the load increases, there will be relativemovement between the cams and the spring pressed arms with the resultthat the driven shaft will rotate at a slower speed than that of thedriving shaft. Under these conditions, the spring pressed arms willimpart a succession of forwardly directed impulses to the cam membersand the torque applied to or available at the driven shaft will beincreased, the magnitude of the impulses and the amount by which thetorque "is increased being dependent upon the settings of the cammembers.

As mentioned previously, the unit is reversible. i. e. either shaft I orthe shaft I6 may be driven, providing that the direction of rotation toproduce an increase of torque is such that the relative motion betweenthe cam. members and the arms causes the latter to move up the steepercam portions A and that a momentum or kinetic energy storing element isassociated with the driving member.

In order to provide for the relative displacements of the cam members,bevel teeth 20 are provided on the inner side faces of the cams I2 andI4 so that they are adapted to engage with a pinion 2| mounted in thecentral hub I5 with its axis of rotation disposed radially of the hub.whilst the cam I3 is rigidly secured to a peripheral portion of the hub.Adjacent to its inner end, the pinion shaft 22 is provided with a wormwheel 23 adapted to co-operate with a worm 24 provided upon a spindle 25rotatably mounted in the hub I5 with its axis of rotation disposedparallel with the driven shaft I6. By rotating the spindle 25, the camsl2 and M can be displaced relatively to the cam |3 by predeterminedamounts dependent upon the maximum torque setting required. In instanceswhere it is required to provide a transmission unit for greater torqueratios, the lengths of the cam portions vA are decreased and the lengthsof the cam portions B are increased so that the ratio of the sum of thelengths of the cam portions, A and B to the lengths of the portions Acorresponds substantially with the ratio ofthe torque required and 'thenumber of sets of cams to be provided for the operation of the unit.With these conditions the mean torque supplied to the cams willcorrespond with the normal torque available at the driving'shaft.

In some instances, means responsive to the speed fluctuations of thedriven shaft may be provided for automatically adjusting the maximumtorque settings of the cams under the varying load conditions. Oneconvenient means suitable for this purpose is diagrammaticallyillustrated in Figs. 3 and 4. To the outer end of the spindle 25 issecured a gear wheel 28 adapted to mesh "with another gear wheel 29keyed to a spindle 30 on which is also keyed a further toothed wheel 3|.The spindle 30 is rotatably mounted in a pair of parallel arms 32 whichare pivotally mounted on the worm spindle 25 and with free ends of whichare associated a weight 34 and a spring 35, the latter being so arrangedthat it tends to move the weight and the arms inwardly and being soproportioned that, as the speed of the driven shaft I6 varies, the arms32 will be moved upon their pivotal supports in a direction and to anextent dependent upon the resultant of the centrifugal forces and thetension of the spring. Thus, when the speed of the driven shaft l6exceeds a predetermined maximum value, the weight and the arms will bemoved outwardly away from' the centre of rotation of the driven shaft bythe predominating centrifugal force produced, Whilst, when the speed ofthe driven shaft is less than the predetermined minimum' value, theweight and the arms will be caused to move inwardly towards the centreof rotation. Upon a fixed member 37, which may be convenientlyconstituted by a part of the casing of the transmission unit, areprovided a pair of radially displaced pins 38 and 39, the arrangementbeing such that, when the speed of the driven shaft Hi reaches thepredetermined maximum value, the teeth of the wheel 3| will engage thepin 38 and thus cause the wheel 3|, the gears 29 and 28 and the wormspindle 25 to be displaced angularly by predetermined amounts. Also,when the speed of the, driven shaft reaches the predetermined minimumvalue, the teeth of the wheel 3| will engage the pin 39 and thus causeangular displacements of the wheel 3|, the gears 29 and 28 and the wormspindle 25 in the opposite direction. The thread of the worm 24 is suchthat, when the teeth of the wheel '3|- engage the outer pin 38, thecains are displaced relatively to one another in such a manner that themaximum torque setting or the torque delivered to or available at thedriven shaft is reduced. On the other hand, when the teeth of the wheel3| engage the inner pin 39, the cams are displaced in the oppositedirection so that they more nearly coincide and the maximum torquesetting or the torque delivered to the driven shaft is increased.

Upon the pivoted ends of the arms 32 is provided a shorter arm orprojection 40, and fixed to the cam I2 are two angularly displaced pins4| and 42. In the arrangement herein described, the cam |2 may be movedin a counter-clockwise direction when the torque required to drive theshaft |6 is being reducedand the pin 42 is so arranged that, when thecam l2 has reached the limiting position for providing a substantiallydirect drive, the pin will engage the projection 40 and cause the arms32 to be moved about theinpivots in a counter-clockwise direction, i. e.in the opposite direction to that produced by the centrifugal forces onthe weight 34, sothat the wheel 3| is moved to such a position that itwill no longer be acted upon by the outer pin 38. This position will bemaintained until the shaft Hi again requires a; larger torque when thespeed'of the driven shaft will be decreased and, consequently, the.tension of the spring will exceed the centrifugal forces on the weight34 and the toothed wheel 3| will engage the inner pin 39 as abovedescribed and thereby cause a displacement of the cam |2 in a clockwisedirection to increase the torque applied. Also, in the limiting maximumtorque setting position, the pin 4| will engage the projection and causea displacement of the arms 32 so that the wheel 3| is moved to aposition at which it is no longer acted upon by the inner pin 39.

Fig. 5 shows one convenient form of a manually operable means which maybe employed for adjusting the maximum torque settings of the cams duringthe operation of the transmission mechanism. In this arrangement, theouter end of the worm spindle 25 is provided with a worm wheel 45adapted to co-operate with a worm 45 mounted upon a shaft 41 carried bya casing 48 which forms a housing for the worm spindle 25 and which issuitably secured to the side of the central hub |5. To the free or aprojecting end of the shaft 41 is secured a toothed wheel 50 arranged toco-operate with a longitudinally displaceable sleeve 5| mounted upon thedriven shaft I6. The said sleeve is provided on its periphery with aseries of circumferential grooves forming a series of parallel teeth 52arranged in planes at right angles to the axis of the shaft l6, whichteeth are adapted to engage with those formed upon the wheel 50. Also,adjacent to its outer end the sleeve is formed with a circumferentialgroove 53 to receive the rounded end of an arm 54 pivotally mounted at55 upon a bracket 56 provided upon the casing 51, the arrangement beingsuch that the lower end of the arm 54 can be caused by manually operablemeans to move substantially parallel with the axis of the shaft l6 toeffect a displacement of the sleeve 5|. By this arrangement, the sleevemay be displaced and the worm spindle 25 rotated to cause an adjustmentof the relative positions of the cam members during the operation of themechanism. I

It is to be understood that the invention is not restricted to thedetails of construction herein described and illustrated but thatvarious changes or modifications may be made without departing from theinvention as defined by the appended claims.

Having thus described my invention what I claim as new therein anddesire to secure by Letters Patent is:--

1. A power transmission mechanism comprising a driving member, a memberto be driven, a

plurality of cam members carried by one of the members and a pluralityof loaded arms carried by the other member and adapted to coact withraised portions provided on the cam members in aflording a drivingconnection between the driving and the driven members, the arrangementbeing such that, when the load is light, the driving member and thedriven member will rotate at substantially the same speed withsubstantially norelative movement between the cam members and the armswhilst, when the.load increases, relative movement occurs between thecam members and the arms in such a manner that a succession o1 forwardlydirected impulses are imparted to the driven member and the torqueavailable thereat is increased and also such that the cam members can bedisplaced angularly relatively to one another so as to vary theirmaximum torque settings. 1

2. A power transmission mechanism comprising the combination of adriving member, a driven member, a plurality of cams coupled to one o!the members, a plurality ot loaded elements moving with the other memberso as to coact with the cams in aflording a driving connection betweenthe driving and the driven memhers and a spring loaded centrifugaldevice subiect to the speed fluctuations or the driven member andadapted to cause an element carried thereby to coact with one o! a pair01' stationary stops whenever the speed reaches a limiting value, thesaid element being interconnected with means for adjusting the maximumtorque setting of the mechanism.

3. A power transmission mechanism comprising the combination of adriving member, a driven member, a plurality of cams coupled to one ofthe members, a plurality of loaded elements moving with the other memberso as to coact with the cams in affording a driving connection betweenthe driving and the driven members, gear teeth upon certain of the camsand means responsive to the speed fluctuations ot the driven member forcausing the displacement of an element engaging said gear teeth to movethe cams relatively to one another.

4. A power transmission mechanism comprising the combination of adriving member, a driven member, a plurality, of cams coupled to one ofthe members, a plurality of loaded elements moving with the other memberso as to coact with the cams in affording a driving connection betweenthe driving and the driven members, a centrifugal device subject to thespeed fluctuations of the driven member and adapted to cause an elementcarried thereby to coact with one of a pair of stationary stops wheneverthe speed reaches a limiting value, the element being inter-connectedwith means for relatively moving said cams, and further stops carried bya cam member and adapted to adjust the position of the element carriedby the centrifugal device when the cam member reaches a limitingposition.

CECIL CHARLES MORLEY.

